@mixin bg($url) {
  background: url($url) no-repeat;
  background-size: 100% 100%;
}

@mixin center {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

// 宽高
@mixin wh($width, $height) {
  width: $width;
  height: $height;
}

// 宽最小高
@mixin wmh($width, $height) {
  width: $width;
  min-height: $height;
}

// 字体大小，颜色
@mixin sc($size, $color) {
  font-size: $size;
  color: $color;
}